WASHINGTON - Vaccine advisers to the US Centers for Disease Control and Prevention (CDC) voted unanimously Thursday to recommend the Pfizer-BioNTech and Moderna COVID-19 vaccines be preferred over the Johnson & Johnson vaccine due to very rare but dangerous blood clot risk.

A total of 54 cases of thrombosis-thrombocytopenia syndrome (TTS), a rare and severe type of blood clot, had been reported from March through August in the United States out of 14.1 million Johnson & Johnson vaccine doses administered, according to data presented by the CDC's Advisory Committee on Immunization Practices.

The highest rates, nearly 20 percent, happened in the recipients aged between 30 to 49. A total of 26 cases are women aged under 50. About 80 percent of the cases were in white non-Hispanic persons, according to CDC data.

A total of nine deaths from the TTS had been reported through Dec. 9, seven female and two male. All of them are all non-Hispanic white, CDC data show.

The overall death reporting rate is 0.57 per million Johnson & Johnson vaccine doses.

The Johnson & Johnson single-dose vaccine has been linked to TTS which halted its use for 10 days in April. The pause was lifted after the US Food and Drug Administration (FDA) conducted a safety review.

Back then, the FDA and the CDC had determined the available data show that the vaccine's known and potential benefits outweigh its known and potential risks in individuals 18 years of age and older.

The majority of COVID-19 vaccines given in the United States are Pfizer-BioNTech and Moderna, with about 284 million Pfizer-BioNTech doses and 186.4 million Moderna doses administered by Dec. 15, according to CDC data.

About 17.2 million Johnson & Johnson shots have been administered since it was approved for emergency use in the United States in late February, CDC data show.